i have an 4x4 2006 tacoma SR5and i am looking to put a locker on my tacoma, but i do not know if its a smart idea. what are the pro's and con's on having them on and how would i find out which one i need? I really need help with this delima.

But if you are chosing a locker you might want to choose a selectable locker. Like an ARB air locker. So your differential is open for easy street driving and you can lock it when you are offroad and in the shit.

Edit: But to answer your original question. Yes it is smart to have a locker.... if you offroad allot.

ARB air lockers are rated near the top, if not the top.
Lockers are great for rock crawling and when you are stuck in the mud.
But on the road you turn them off and leave them off.
On Toyotas, I think their A-trac system is even better for city driving/getting stuck in the mud.
Look up A-trac on this site to see how it works.
Good luck with your choice.

Depends who you are. Your trucks road manners will go out the door. I have friends with miller locked rears and they bark there tires around every turn, and when its wet the rear end tends to kick out more then a open diff.

Thats why a selectable locker is best for the street. Open when you want, locked when you want.